<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="start.js"></script>
    <script>
        console.log("hello world");
        function f1(msg) {
           alert(msg);
        }
    </script>
</head>
<body>
<!--在按钮上注册点击事件-->
<button onclick="alert('hello button1')">button1</button>
<button onclick="f1('hello button2')">button2</button>
<button onclick="f2('hello button3')">button3</button>
</body>
</html>